// SPDX-License-Identifier: ISC
/*
 * Copyright (c) 2021-2025 Yahweasel
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

onmessage = (ev) => {
  /* Message is the buffer the write head. Wait for the write position to
   * change. */
  const buf = ev.data;
  let prevVal = Atomics.load(buf, 0);
  while (Atomics.wait(buf, 0, prevVal)) {
    const newVal = Atomics.load(buf, 0);
    if (prevVal !== newVal) {
      postMessage([prevVal, newVal]);
      prevVal = newVal;
    }
  }
};
